Tyre, wheel, method and system for monitoring the tyre, and method for controlling a vehicle

ABSTRACT

A method for monitoring a tire during running includes acquiring and storing, at least temporarily, a first curve representing an acceleration profile of a first point of a tread area of the tire; acquiring and storing, at least temporarily, at least one second curve representing an acceleration profile of a second point of the tread area; and comparing the first curve and the at least one second curve, or parameters derived from the first curve and the at least one second curve, so as to determine a dynamic behavior of the tire. The first and second points are located substantially on a same meridian plane of the tire. A related tire, wheel for a vehicle, system for monitoring a tire during running, and method for controlling a vehicle are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national-phase entry under 35 U.S.C. § 371 fromInternational Application No. PCT/EP03/03088, filed Mar. 25, 2003, inthe European Patent Office, the content of which is relied upon andincorporated herein by reference; additionally, Applicants claim theright of priority under 35 U.S.C. § 119(a)-(d) based on InternationalApplication No. PCT/EP02/03498, filed Mar. 28, 2002, in the EuropeanPatent Office.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for monitoring thebehavior of a tyre during the running of a motor vehicle equipped withtyres. The present invention relates also to a method for controlling avehicle.

2. Description of the Related Art

Tyre monitoring systems using accelerometers disposed within tyres havealready been proposed.

EP patent application no. 887,211 describes a tyre monitoring system fora tyre on a vehicle comprising: a sensor device operatively arrangedwith respect to the tyre to create an electrical pulse during thefootprint pass corresponding to a deformation of the tyre; means forcalculating a ratio of the duration of said electrical pulse to theduration of one tyre revolution; means for transmitting said ratio to anevaluating unit placed in the vehicle. The sensor device is placedwithin the tread area of said tyre in order that said electrical pulsepresents a first maximum at the entrance and a second maximum at theleaving of said footprint pass. The sensor device can be anaccelerometer that measures the intensity of the acceleration supportedby the tread. The aim of the solution disclosed in the '211 patentapplication is the monitoring of the tyre deflection in order to obtainan optimum performance, particularly for truck tyres.

U.S. Pat. No. 6,204,758 describes a tyre monitor for use in a remotetyre monitor system including an accelerometer for detectingacceleration of the tyre monitor. Position information for the tyremonitor is determined in response to the acceleration. In this manner,tyre position information is determined automatically to allow thesystem to display tyre characteristic data such as air pressure inconjunction with tyre position. More particularly, the tyre monitorincludes a housing and a valve stem and is configured for mounting on awheel of a vehicle. The valve stem opens to admit air for filling thetyre and for manual checks of the tyre pressure. Otherwise, the valvestem generally remains closed to seal the tyre. The tyre monitorincludes a radial accelerometer, a tangential accelerometer, a yawaccelerometer, and a pressure sensor.

PCT patent application no. 98/56606 discloses a method for monitoring arunning motor vehicle tyre, and, in particular, a device comprising: asensor mounted on the wheel, coupling means transmitting to the vehicleindications obtained from the sensor and power supply means. The sensoris a miniature sensor sensitive to acceleration, implanted in the tyrerunning tread or in proximity thereof. The coupling means, mounted onthe wheel, transmit the indications relative to the measurements carriedout when the running tread is in contact with the ground. Moreparticularly, the authors consider a tyre having a radius R traveling ata speed V. A tyre portion BC, having a length L, is in contact withground, under load. In a point A, outside the portion BC, thecentrifugal radial acceleration is V²/R. On the other hand, between thepoints B and C the centrifugal radial acceleration is substantiallyzero, in that the differential speed of the tyre with respect to theground is substantially zero. By implanting an accelerometer within thetyre, the portion BC can be detected. The aim disclosed by the authorsfor such kind of measurement is to detect a possible under-inflation ofa tyre.

SUMMARY OF THE INVENTION

The Applicant has faced the problem of monitoring the dynamic behaviorof a tyre mounted on a vehicle. More particularly, the Applicant hasfaced the problem of deriving information from a rolling tyre mounted ona vehicle, the information being useful:

-   -   a) to identify the manoeuvre that is being executed by the        vehicle (e.g. cornering, braking, etc.);    -   b) to reveal whether a critical condition is being reached        during said manoeuvre;    -   c) in case b), to generate a signal adapted to cause a        counteraction to control the vehicle, e.g. an alarm signal for        the driver or a signal adapted to activate an auto-control        system of the vehicle.

The Applicant has found that measurements performed by accelerationsensors disposed in correspondence of the tread area of the tyre allowto derive such information. More particularly, the Applicant has foundthat such information can be derived by at least two accelerationsensors, disposed substantially along the same meridian plane of thetyre (i.e., a plane including the rotation axis of the tyre), incorrespondence of the tread area of the tyre. The acceleration sensorsprovide signals representative of the deformations in the wholeinteraction region between the tyre and the ground. An analysis of thevariations during time of the deformations then allows to identify themanoeuvre being performed. In a preferred embodiment, three accelerationsensors are disposed substantially on the same meridian plane incorrespondence of the tread area of the tyre, a first one being disposedsubstantially on the equatorial plane of the tyre and the other twobeing disposed in shoulder regions of the tread area (i.e., portions oftread area disposed between the equatorial plane and the sidewalls ofthe tyre).

In a first aspect, the invention relates to a method for monitoring atyre during running, said tyre having a tread area, the methodcomprising the steps of:

-   -   acquiring and storing, at least temporarily, a first curve        representing an acceleration profile of a first point of the        tread area of said tyre, located on a meridian plane of said        tyre;    -   acquiring and storing, at least temporarily, at least a second        curve representing the acceleration profile of a second point of        the tread area of said tyre, located substantially on said        meridian plane;    -   comparing said first and second curves, or parameters derived        thereof, so as to determine a dynamic behavior of said tyre.

Preferably, the method further comprises the step of:

-   -   acquiring and storing, at least temporarily, at least a third        curve representing the acceleration profile of a third point of        the tread area of said tyre, being located substantially on said        meridian plane.

The step of comparing may comprise comparing said first, second andthird curves, or parameters derived thereof.

Preferably, said first point is located in a first shoulder region ofsaid tread area.

Advantageously, said second point is located in a second shoulder regionof said tread area, opposite to the first shoulder region with respectto an equatorial plane of said tyre.

The above cited third point may be located substantially on theequatorial plane of said tyre.

In preferred embodiments, said first, second and third points arelocated on an inner surface of said tyre.

Preferably, said step of comparing comprises comparing a distancebetween characteristic peaks of said first curve with a distance betweencorresponding peaks of said second curve.

Alternatively, said step of comparing may comprise comparing said firstcurve and said second curve point by point, for an entire revolution ofsaid tyre.

Alternatively, said step of comparing may comprise comparing at leastone characteristic peak of said first curve with a corresponding atleast one peak of said second curve.

In particular, said step of comparing may comprise comparing anamplitude of said at least one peak of the first curve with an alititudeof said corresponding at least one peak of the second curve.

Alternatively, said step of comparing may comprise comparing an areaunder at least a portion of said first curve with an area under acorresponding portion of said second curve.

Alternatively, said step of comparing may comprise comparing a width ofat least a portion of said first curve with a width of a correspondingportion of said second curve.

In a second aspect, the invention relates to a tyre comprising at leasta first group of sensors located in a first circumferential position ofsaid tyre, said first group of sensors including:

-   -   a first acceleration sensor, associated with a first point of        the tread area of said tyre, located on a meridian plane of said        tyre;    -   at least a second acceleration sensor, associated with a second        point of the tread area of said tyre, located substantially on        said meridian plane.

Preferably, said first group of sensors includes at least a thirdacceleration sensor, associated with a third point of the tread area ofsaid tyre, located substantially on said meridian plane.

Preferably, said first point is located in a first shoulder region ofsaid tread area.

Advantageously, said second point is located in a second shoulder regionof said tread area, opposite to the first shoulder region with respectto an equatorial plane of said tyre.

The above cited third point may be located substantially on theequatorial plane of said tyre.

In preferred embodiments, said first, second and third points arelocated on an inner surface of said tyre.

In particular, said first, second and third points may be misaligned ofan angle not greater than 5°, preferably not greater than 3°, morepreferably not greater than 1°.

Preferably, said first and second points are located at a distance fromthe equatorial plane of the tyre comprised between 15% and 30%, morepreferably between 18% and 28%, even more preferably 20% and 25% of thewhole tread width.

The tyre according to the second aspect of the invention may furtherinclude at least a second group of said sensors, located in a secondcircumferential position of said tyre, spaced from said firstcircumferential position of a predetermined angle.

In a preferred embodiment, the tyre according to the second aspect ofthe invention further includes at least a third group of said sensors.The first, second and third group of sensors are spaced one from eachother of substantially the same angle.

Each of said acceleration sensors may include an elaboration unit.

In a third aspect, the invention relates to a wheel for a vehicle,including a rim and a tyre. With regards to the tyre, reference is madeto what said above.

The wheel may also include a further acceleration sensor associated withsaid rim.

In a fourth aspect, the invention relates to a system for monitoring atyre during running, including a tyre comprising at least a first groupof sensors, and a receiving unit associated with at least said firstgroup of sensors, said first group of sensors including:

-   -   a first acceleration sensor, associated with a first point of        the tread area of said tyre, located on a meridian plane of said        tyre;    -   at least a second acceleration sensor, associated with a second        point of the tread area of said tyre, located substantially on        said meridian plane.

The receiving unit may comprise a receiver and an elaboration unit.

With regards to the tyre included in the system, reference is made towhat said above.

In a fifth aspect, the invention relates to a method for controlling avehicle, comprising the steps of:

-   -   providing, in at least one tyre mounted on the vehicle, at least        a first group of sensors including at least a first acceleration        sensor, associated with a first point of a tread area of said        tyre, and at least a second acceleration sensor, associated with        a second point of said tread area, said first and second points        being both located substantially on a same meridian plane of        said tyre;    -   acquiring and storing, at least temporarily, at least a first        acceleration curve from said first acceleration sensor and at        least a second acceleration curve from said second acceleration        sensor;    -   comparing said first and second curves, or parameters derived        thereof;    -   identify a manoeuvre of said vehicle from said comparison.

The method may further include the steps of:

-   -   revealing, from said comparison, whether a critical condition is        being reached during said manoeuvre;    -   if a critical condition is being reached, generating a signal        adapted to cause a counteraction to control the vehicle.

In one embodiment, said signal may be adapted to activate an alarm for adriver of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

In another embodiment, said signal may be adapted to activate anauto-control system of the vehicle.

Characteristics and advantages of the invention will now be illustratedwith reference to embodiments represented in the attached figures, inwhich:

FIG. 1 schematically shows a transverse section of a tyre having threeacceleration sensors disposed on the liner internal surface, accordingto a preferred embodiment of the present invention;

FIG. 2 schematically shows an equatorial section of a tyre having threegroups of acceleration sensors disposed on the liner internal surface,according to a further preferred embodiment of the present invention;

FIG. 3 shows three plots of contact length versus number of wheel turnsfor a cornering tyre, the contact length being calculated frommeasurements of tangential acceleration in a tyre configurationaccording to FIG. 1;

FIG. 4 shows a typical curve derived by a measurement of tangentialacceleration;

FIG. 5 shows two curves of centripetal acceleration measured by twoacceleration sensors disposed in the shoulder regions of the tread areaof a tyre, in a cornering condition.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows an exemplary tyre 1 comprising an internally hollowtoroidal structure formed by a plurality of components, and primarily bya carcass, terminating in two beads, each formed along an innercircumferential edge of the carcass, for securing the tyre to acorresponding supporting rim. The tyre 1 typically comprises at leastone pair of annular reinforcing cores, called bead cores, which areinserted in the said beads. The carcass has a supporting structureformed by at least one reinforcing ply which includes textile ormetallic cords, axially extending from one bead to the other accordingto a toroidal profile, the ends of which are associated with acorresponding bead core. In radial tyres, the aforesaid cords lieessentially in planes containing the axis of rotation of the tyre.

In crown of this carcass, an annular structure, known as belt structure,is placed, normally comprising one or more strips of rubberized fabric,wound on top of each other. A tread made from elastomeric material,wound around the belt structure, and usually molded with a reliefpattern for the rolling contact of the tyre with the road is also added.Two sidewalls, made from elastomeric material, each extending outwardsin radial direction from the outer edge of the corresponding bead, arealso placed on the carcass, in axially opposed positions.

In tubeless tyres the inner surface of the carcass is normally coveredwith at least one liner layer, i.e. with one or more layers of airtightelastomeric material. The tyre 1 may further comprise other knownelements, such as edges, strips and fillers, according to the specificdesign of the tyre.

For the purposes of the present description, the term “elastomericmaterial” indicates a material obtained by crosslinking a rubbercomposition comprising at least an elastomeric polymer having at least afiller dispersed therein and usually conventional additives such ascuratives, processing aids, etc. . . . The combination of all theseelements determines the mechanical characteristics of elasticity,rigidity and resistance to deformation of the tyre, which constitute theconnection between the system of forces applied to the tyre and theextent of the corresponding deformations which it undergoes.

One aspect of the present invention relates to the real time measurementof the variations of the acceleration of specified points of a tyre in agiven temporal interval. Said variations are in relationship with theinteractions between the tyre in motion and the ground and are inrelationship with the deformations of the tyre itself during motion. Tothis purpose, at least two sensors able to measure said acceleration aredisposed substantially along the same meridian plane within the tyre 1.For the purposes of the present invention, the expression “substantiallyalong the same meridian plane” contemplates a certain amount ofmisalignment of the acceleration sensors with respect to said meridianplane, that can be expressed in terms of the angle comprised between themeridian planes defined by the acceleration sensor positions.Preferably, the tolerated misalignment may correspond to an angle notgreater than 5°, more preferably not greater than 3°, even morepreferably not greater than 1°. More particularly, the sensors aredisposed in correspondence of the tread area T of the tyre 1, i.e., theportion of the tyre 1 axially extended between the sidewalls of the tyre1 (see FIG. 1). Preferably, at least three acceleration sensors aredisposed along substantially the same meridian plane of the tyre 1.

In the embodiment shown in FIG. 1, three sensors 11, 12, 13 are disposedon the internal surface of the tyre 1, on the inner liner surface. Afirst sensor 11 is disposed substantially along the equatorial plane ofthe tyre 1. Two other sensors 12, 13 are disposed substantially on thesame meridian plane of the tyre 1 in shoulder regions of the tread area,i.e. between the equatorial plane and a respective sidewall of the tyre1. Hereinbelow, they will be named left shoulder sensor 12 and rightshoulder sensor 13. As it will specified in the following, saiddisposition allows to monitor the general behavior of the fullinteraction area between the tyre and the road; for instance when thetyre is cornering the signals derived from the two sensors 12 and 13change relative to each other. In order to ensure a good monitoring ofthe whole interaction area between the tyre and the road, theacceleration sensors should be separated from each other of a certaindistance. However, with regards to acceleration sensors disposed in theshoulder regions of the tread area, they should be disposed sufficientlyfar away from the sidewalls, so that they can provide signals in almostevery condition of travel. In this respect, it has to be noticed thatvehicle regulations, such as for example the camber, in combination withparticular manoeuvres of the vehicle (e.g. in sharp bends) may causetransient partial loss of interaction between portions of the tread nearthe sidewall and the ground. Preferably, a shoulder acceleration sensorshould be disposed at a distance from the equatorial plane of the tyrecomprised between 15% and 30% of the tread width, more preferablybetween 18% and 28% of the tread width, even more preferably between 20%and 25% of the tread width. For example, in a tyre having a tread widthof 195 mm, two shoulder sensors may be disposed on opposite sides withrespect to the equatorial plane, each at a distance of 45 mm thereof.

Preferably, at least one acceleration sensor measures the accelerationof the respective monitored point of the tyre 1 with respect to at leasttwo directions orthogonal to each other. More preferably, allacceleration sensors measure the acceleration with respect to at leasttwo directions orthogonal to each other. For example, in FIG. 1 the x, yand z local axes represent three directions that for the purposes of thepresent description are named respectively:

-   -   centripetal direction z, which is a radial direction of said        tyre,    -   tangential direction y, which is a direction tangential to the        circumference of said tyre,    -   lateral direction x, which is a direction orthogonal to both        said centripetal and tangential directions.

Preferred directions for the measurements are the centripetal and thetangential direction.

In FIG. 2 a further embodiment of the present invention is shown, inwhich several groups of acceleration sensors 21, 22, 23 are associatedto a tyre 1. Each group of acceleration sensors 21, 22, 23 comprisesacceleration sensors disposed substantially along the same meridianplane of the tyre 1, as disclosed above with reference to FIG. 1.Preferably, the groups of acceleration sensors are located in acircumferential position spaced one from each other of substantially thesame angle. For example, in FIG. 2 three groups of acceleration sensorsare shown, spaced from each other of an angle of substantially 120°. Asfar as the disposition of the acceleration sensors within each group 21,22 or 23 in the embodiment of FIG. 2, reference is made to whatdisclosed above with reference to FIG. 1.

The use of plurality of groups of acceleration sensors as shown in FIG.2 allows to achieve more accuracy and reliability of the measurementsperformed by the acceleration sensors, as well as a better monitoring ofthe entire wheel turn. For example, during a revolution of the tyre 1 itis possible to monitor at the same time the acceleration during the tyreground interaction with a first group of sensors, the acceleration of apoint located before the footprint pass with a second group of sensorsand the acceleration of a point located after the footprint pass with athird group of sensors.

The acceleration sensors 11, 12, 13 and/or 21, 22, 23, may be typicallypackaged in respective sensor devices further including: a power supply,such as for example a battery or a self-generating power device (e.g., apiezoelectric device generating electrical energy thanks to thedeformations subjected by the tyre during rotation), for energizing theacceleration sensor; a transmitter connected to the acceleration sensorand to the power supply; an antenna connected to the transmitter.Furthermore, the acceleration sensors 11, 12, 13 and/or 21, 22, 23 aretypically associated with a receiving device, typically including anantenna, a receiver and an elaboration unit. Such receiving device maybe preferably disposed on the vehicle. For example said receiving devicemay be part of an on-board computer of the vehicle.

The acceleration sensors generate a signal correspondent to theacceleration of the respective point of the tyre 1 to which they areassociated. Said signal is then transmitted to the receiver, typicallyby means of radio frequencies. The elaboration unit may comprise, forexample, a programmed microprocessor having a volatile storage element,a permanent storage element and a CPU. The elaboration unit receives theacceleration signals and performs the elaborations needed in order toidentify, from said signals, what kind of manoeuvre (e.g. braking,acceleration, cornering, etc.) is being performed by the tyre or by thevehicle. Furthermore, it can also derive if a critical condition isbeing reached by the tyre or by the vehicle during such manoeuvre (forexample due to aquaplaning). In such case, a signal can be generated, tocause a counter-action to control the vehicle, e.g. by the driver or byauto-control systems of the vehicle.

The elaborations needed in order to identify from the accelerationmeasurements the manoeuvre performed by the tyre, as well as to foreseeif a critical situation is being reached, include the comparison of thesignals measured from two acceleration sensors disposed substantially onthe same meridian plane of the tyre 1. As it will be shown below, ameasurement performed by a single acceleration sensor cannot givesufficient information for the above mentioned purposes.

For example, FIGS. 3 a, 3 b, 3 c show the result of elaborationsperformed on acceleration signals provided by acceleration sensorsdisposed within a tyre as shown in the embodiment of FIG. 1. The threeacceleration sensors were disposed within a 195/65R15 Pirelli™ P6® tyre.The tyre was inflated at a pressure of 2.2 bar, subjected to a load ofabout 3700 N and mounted on the front right axle of a vehicle. Theresult shown by the three curves of FIG. 3 refers to a path covered bythe vehicle at a speed of about 80 km/h, consisting of 150 m of straightroad followed by a curve to the left having a radius of about 120 m.

FIG. 3 a refers to an elaboration made on signals provided by a leftshoulder acceleration sensor 12 (see FIG. 1), FIG. 3 b refers to anelaboration made on signals provided by a central acceleration sensor 11(see FIG. 1), FIG. 3 c refers to an elaboration made on signals providedby a right shoulder acceleration sensor 13 (see FIG. 1). Moreparticularly, the curves of FIGS. 3 a, 3 b, 3 c show the contact lengthderived by a measurement of the tangential acceleration a_(T), versusthe number of turns # performed by the tyre during the above mentionedpath. FIG. 4 shows a magnifying of the portion corresponding to thepassage under the contact length in a typical signal measured by anacceleration sensor in tangential direction (acceleration versus time).By counting the number np_(i) of points in the measured curve betweenthe two discontinuities shown in FIG. 4 (corresponding to the beginningand the end of the passage under the contact length of the measuringacceleration sensor), and knowing the sampling frequency, the radius ofthe tyre and the angular speed of the tyre, it is possible to derive thecontact length, i.e. the quantity plotted in FIGS. 3 a, 3 b, 3 c. Thecontact length may also be derived by measurements of centripetalacceleration, according to the teachings of the above mentioned patentapplications EP 887,211 and WO 98/56606.

Firstly, we consider a single plot among those shown in FIG. 3,corresponding to a measurement derived by a single acceleration sensordisposed within the tyre, for example the plot of FIG. 3 b, derived bymeasurements performed by an acceleration sensor disposed at theequatorial plane of the tyre. As results from that plot, the contactlength remains substantially unchanged around 125 mm in the firstportion of the plot, and increases up to a value of about 140 mm in thesecond portion. The beginning of the increase in the contact lengthcorresponds to the beginning of the curve during the traveled path.However, from the curve shown in FIG. 3 b alone, unique informationabout what kind of manoeuvre (a cornering, in this case) is beingperformed by the vehicle cannot be derived. As a matter of fact, theincrease in the contact length shown in FIG. 3 b could correspond to anincrease of the load charged on the wheel carrying the tyre, for exampledue to a braking, or, as another example, to a reduction of the pressurewithin the tyre. Thus, complete information allowing to identify thecorrect manoeuvre cannot be derived from the measurement of a singleacceleration sensor.

On the contrary, by comparing the three curves of FIG. 3, the corneringof the vehicle can be detected. In fact, in the first portion of theplots of FIG. 3 a, 3 b, 3 c, corresponding to the straight portion ofthe traveled path, the contact length derived by the measurementsperformed by the right shoulder acceleration sensor is lower than thecontact length derived by measurements performed by the otheracceleration sensors, due to the camber regulation of the vehicle. Atthe beginning of the curved portion of the traveled path, in the centralportion of the plots 3 a, 3 b, 3 c, different variations in the contactlength can be observed: in particular, a strong increase of the contactlength measured by the right shoulder acceleration sensor, as aconsequence of the lateral thrust to which the vehicle is subjectedduring the curved traveled path. These differences in the measurementsperformed by the three acceleration sensors disposed according to theembodiment shown in FIG. 1 allow to detect, by means of a comparisonbetween the signals or between the parameters derived from the signals(e.g., the contact length), the cornering manoeuvre of the vehicle.Furthermore, the comparison can reveal whether a critical condition isbeing reached, corresponding to abnormal differences between thedetected signals or parameters in the detected manoeuvre.

Many types of comparisons can be performed from signals obtained by thedifferent acceleration sensors included within the tyre, according tothe present invention. Examples of comparisons between accelerationcurves of acceleration versus time obtained by the different sensorscomprise the following:

-   -   comparison of two curves completely point by point, for an        entire revolution of a tyre;    -   comparison of some characteristic peaks of a first curve with        correspondents characteristic peaks of a second curve, with        particular reference to peak amplitudes;    -   comparison of the entire area under a first curve (or under a        portion thereof) with the corresponding entire area under a        second curve (or under the corresponding portion thereof;    -   comparison of the width of a portion of a first curve with the        width of a corresponding portion of a second curve.

The information obtained from said comparisons can be used to setcontrol actions of mechanisms of the motor vehicle, for exampleregulation of the brake system (longitudinal behavior and/or lateralone), or active suspension, etc.

In a preferred embodiment, an elaboration unit may be disposed alsowithin each sensor device, associated to the respective accelerationsensor, so that already pre-elaborated signals can be sent to thereceiving device disposed on the vehicle. In this case, the elaborationunit of the receiving device collects the pre-elaborated signals comingfrom all the acceleration sensors and performs the needed comparisonbetween the different pre-elaborated signals, according to theinvention. For example, such pre-elaborated signals may compriseparameters derived from the acceleration curves (such as, for example,peak amplitudes or peak-to-peak distances).

In preferred embodiments, the sensor devices including the accelerationsensors 11, 12, 13 and/or 21, 22, 23 are disposed on the internalsurface of the tyre, in contact with the liner layer. Such dispositionis preferred because a precise control of the position of the sensorsmay be achieved, together with a simple installation process. Thesensors 11, 12, 13 and/or 21, 22, 23 may be associated to the innerliner surface by means of an adhesive or by mechanical means.Alternatively, one or more of said acceleration sensors may be insertedinto the liner layer, or into the tread band layer, or into the carcass,or into the belt of the tyre during the manufacturing process.

In a further embodiment (not shown), at least one further accelerationsensor may be disposed in a sensor device placed on the rim of thewheel; in this case a comparison between the acceleration measured bythe rim sensor and the acceleration measured by a sensor located incorrespondence of the tread area may give an indication of the relativemovement between the rim and the tyre for example during a brakingmanoeuvre.

The number and the arrangement of acceleration sensors to be disposedwithin the tyre depends on the specifications to be met. Generallyspeaking, a higher number of sensors corresponds to a better monitoring.However, a trade-off with costs, total added weight, elaborationrequirements/capacity etc. should be taken also into consideration.

For example, FIG. 5 shows the acceleration curves measured incentripetal direction by two acceleration sensors disposed in the rightand in the left shoulder portion of the tread area of a 205/55/R16Pirelli™ P7® tyre, inflated at a pressure of 2.2 bar, subjected to aload of 4500 N. This corresponds to the embodiment of FIG. 1, in whichthe central acceleration sensor 11 is removed. The first curve,referenced as S1 in FIG. 5, refers to the right shoulder sensor 13 ofFIG. 1; the second curve, referenced as S2 in FIG. 5, refers to the leftshoulder sensor 12 of FIG. 1. The exemplary tyre was in a left corneringcondition of 3°, at a speed of 120 km/h.

As it can be seen, the right shoulder sensor (curve S1), in a regionthat contains the contact length of the tyre (including the peaksvisible in FIG. 5), measures an acceleration which is greater than theacceleration measured from the left shoulder sensor (curve S2). This isdue to the deformation of the tyre during the cornering condition. Bymonitoring the difference between the accelerations measured from saidtwo sensors the system of the present invention is able to detect acritique condition during a cornering manoeuvre. For example saidcritique condition may be detected by comparing said difference ofaccelerations with a predetermined threshold value or by comparing(point to point) a curve monitored by the shoulder sensors withreference curves stored into one of said memory elements. Specifiedreference acceleration curves, or specified threshold values ofparameters to be derived from the acceleration curves, may be stored inthe volatile storage element or in the permanent storage element of theelaboration unit, in a temporary or permanent way respectively. Thereference curves or threshold parameters may be stored during a setupphase of the system and may be generated by each of the accelerationsensors of the system.

Other information may be obtained by comparing signals derived fromsensors associated to different tyres of a vehicle. For example, inorder to completely monitor a braking of a vehicle, a comparison betweensignals derived from sensors of the front tyres and signals derived fromsensors of the rear tyres of the vehicle may be realized. Anotherexample of a comparison between signals derived from sensors located indifferent tyres of the vehicle may be accomplished during a corneringcondition, in which the difference between signals derived from a tyreon one side of the vehicle may be compared with signals derived from atyre on the other side of the vehicle.

The different acceleration curves are acquired during the running of themotor vehicle on the road, preferably at each revolution of the tyre.The curves (or the values of the parameters derived from characteristicsportions of the curves, such as for example the peak values) may bestored temporarily to carry out the comparison with each other.Furthermore, the curves or the parameters acquired or derived in arevolution of the tyre may be compared with the curves or parametersacquired or derived in previous revolutions of the tyre, or during thecontact of previous portions of the tyre with the ground (see FIG. 2).In this way, a complete monitoring of the behavior of the vehicle can beperformed. Furthermore, main changes during the tyre life (e.g. due towear or structural modification of the tyre) can also be detected, bycomparing the different curves or the parameters generated by the sensorsignals at different times (e.g., monthly).

Advantageously, the accelerations of the monitored points may beintegrated with other information of the vehicle, for example the speedof the vehicle and/or the tyre pressure.

1. A method for monitoring a tyre during running, comprising: acquiringand storing, at least temporarily, a first curve representing anacceleration profile of a first point of a tread area of the tyre;acquiring and storing, at least temporarily, a second curve representingan acceleration profile of a second point of the tread area; andcomparing the first curve and the second curve, or parameters derivedfrom the first curve and the second curve, so as to determine a dynamicbehavior of the tyre; wherein the first and second points are locatedsubstantially on a same meridian plane of the tyre.
 2. The method ofclaim 1, further comprising: acquiring and storing, at leasttemporarily, a third curve representing an acceleration profile of athird point of the tread area; wherein the third point is locatedsubstantially on the same meridian plane of the tyre.
 3. The method ofclaim 2, further comprising comparing the first curve, the second curve,and the third curve, or parameters derived from the first curve, thesecond curve, and the third curve, so as to determine a dynamic behaviorof the tyre.
 4. The method of claim 1, wherein the first point islocated in a first shoulder region of the tread area.
 5. The method ofclaim 4, wherein the second point is located in a second shoulder regionof the tread area, and wherein the second shoulder region is opposite tothe first shoulder region with respect to an equatorial plane of thetyre.
 6. The method of claim 2, wherein the third point is locatedsubstantially on an equatorial plane of the tyre.
 7. The method of claim2, wherein the first, second, and third points are located on an innersurface of the tyre.
 8. The method of claim 1, wherein comparing thefirst curve and the second curve, or parameters derived from the firstcurve and the second curve, comprises comparing a distance betweencharacteristic peaks of the first curve with a distance betweencorresponding peaks of the second curve.
 9. The method of claim 1,wherein comparing the first curve and the second curve, or parametersderived from the first curve and the second curve, comprises comparingthe first curve and the second curve point-by-point for an entirerevolution of the tyre.
 10. The method of claim 1, wherein comparing thefirst curve and the second curve, or parameters derived from the firstcurve and the second curve, comprises comparing one or morecharacteristic peaks of the first curve with a corresponding one or morepeaks of the second curve.
 11. The method of claim 1, wherein comparingthe first curve and the second curve, or parameters derived from thefirst curve and the second curve, comprises comparing an amplitude ofone or more characteristic peaks of the first curve with a correspondingamplitude of one or more peaks of the second curve.
 12. The method ofclaim 1, wherein comparing the first curve and the second curve, orparameters derived from the first curve and the second curve, comprisescomparing an area under at least one portion of the first curve with anarea under a corresponding at least one portion of the second curve. 13.The method of claim 1, wherein comparing the first curve and the secondcurve, or parameters derived from the first curve and the second curve,comprises comparing a width of at least one portion of the first curvewith a width of a corresponding at least one portion of the secondcurve.
 14. A method for controlling a vehicle, comprising: providing afirst group of sensors in at least one tyre mounted on the vehicle;acquiring and storing, at least temporarily, a first acceleration curvefrom a first acceleration sensor and a second acceleration curve from asecond acceleration sensor; comparing the first acceleration curve andthe second acceleration curve, or parameters derived from the firstacceleration curve and the second acceleration curve; and identifying amaneuver of the vehicle based on the comparison; wherein the first groupof sensors comprises: the first acceleration sensor; and the secondacceleration sensor; wherein the first acceleration sensor is associatedwith a first point of a tread area of the tyre, wherein the secondacceleration sensor is associated with a second point of the tread area,and wherein the first and second points are located substantially on asame meridian plane of the tyre.
 15. The method of claim 14, furthercomprising: revealing, from the comparison, whether a critical conditionis being reached during the maneuver; and if a critical condition isbeing reached, generating a signal adapted to cause a counteraction tocontrol the vehicle.
 16. The method of claim 15, wherein the signal isadapted to activate an alarm for a driver of the vehicle.
 17. The methodof claim 15, wherein the signal is adapted to activate an auto-controlsystem of the vehicle.